Constant pressure variable demand hydraulic system



United States Patent CONSTANT PRESSURE VARIABLE DEMAND HYDRAULIC SYSTEM Paul Antalilr, Liberty Township, Trumbull County, Ohio,

assignor to United States Steel Corporation, a corporation of Delaware Filed Oct. 6, 1964, Ser. No. 401,871 4 Claims. (Cl. 23450) The present invention relates generally to hydraulic systems and, more particularly, has as its primary object the provision of an improved multiple-outlet, variable demand water spray system which is shock-free and through which water flows at a constant pressure regardless of the demand on the system.

The system of the invention is especially suitable for use in a hot-metal rolling mill, such as a billet-rolling mill, for descaling the product as it passes through the successive roll stands of the mill. Accordingly, an examplary embodiment of the invention in such use will be described.

Prior to my invention, a typical descaling system of a hot-metal rolling mill included a battery of fluid pumps; a large hydro-pneumatic accumulator to absorb system shock and provide a reservoir of water; a high-pressure air compressor for charging the accumulator; a complex accumulator level control system; a large automatic safety shut-off valve to prevent the accumulator from losing its air charge; and several protective control devices to protect the accumulator and piping system from developing pressures above their capacities. A description of one type of such a system is in the 1941 Modern Strip Mill manual published by the Association of Iron and Steel Engineers (pages 95 through 100).

Such a system not only required a large captial outlay for installation and maintenance but even after installation did not efliciently perform the functions it was intended to. For example, such a system proved unable to maintain a constant descaling pressure under varying water flow demands occasioned by the constantly varying numbers and combinations of descaling water outlets demanding water during rolling operations. This was due to the fact that the delivery presure from a fluid pump varies widely as the water demand from the pump increases or decreases. The accumulator of the system had little ability to correct this pressure variation since it was only a cushioning device intended primarily to absorb system shocks when the water demand was drastically reduced and the pumps continued to deliver water. These variations in descaling pressures produced a wide variation in the amount of descaling of the surfaces of the product being rolled. This resulted in rolled-in-scale on the poorly-descaled portions so that a product having a poor and irregular steel surface was created.

Although the primary function of the accumulator of the system, with its numerous appurtenances, was to protect the system from shock waves, it was only partially effective in doing so. The hydraulic shock pressures which the accumulator was supposed to eliminate adversely affected pipes and valves long before the shock wave reached the accumulator since the descaling valves are necessarily located near the roll stands, remote from the accumulator, with long lengths of piping between them and the accumulator.

The system of the invention proposes to eliminate the foregoing and other disadvantages which were inherent in constant-pressure, variable demand hydraulic systems prior to my invention by providing a unique arrangement of conduits and valves through which fluid received from a pump flows constantly at a substantially unvaried rate and uniform pressure notwithstanding volume of demand.

Other objects and advantages will appear hereinafter 3,261,556 Patented July 19, 1966 from the following description and the accompanying drawing.

In the single figure of the drawing, which is for illustrative purposes only, a hydraulic system embodying my invention is illustrated diagrammatically in perspective.

Referring more particularly to the drawing, reference numeral 2 designates a pump for supplying water under a constant, predetermined pressure to a header 4, which is provided with three outlets 6. If desired, a battery of pumps, which can be of any suitable type such as centrifugal, reciprocating, etc., may be used in place of a single pump. A water spray system, designated generally by reference numeral 8, is connected with each of the outlets 6 for descaling billets B being rolled on a hot rolling mill. In the diagrammatic illustration of the drawing, the spray system at each end is shown in operative descaling condition, while the intermediate system is shown in non-operating condition.

The three spray systems 8 are similar in operation and construction; and each includes a two-position, threeconnection directional fluid valve 10 operated by a springreturn solenoid 12. Each of the valves 10 is provided with an inlet port 14 and two outlet ports 16 and 18 and is so con-tructed that the water flow therethrough is not appreciably diminished or varied when the valve is shifted from one of its open positions to the other so that water pressure is the same at either of the outlet ports. One valve of this type which is available on the market is manufactured by BellowsValvair of Salem, Ohio, and is designated Hunt Double Two-Way Continuous Flow Descaling Valve, Series FOModel No. MSl259-PD2-l5X50484.

A conduit 20 having a filter 22 and a gate valve 24 disposed therein connects each of the valves with an outlet 6 of the header 4. A condiut 26 connects the valve 10 of each of the water spray systems 8 with a spray nozzle head 28 having spray openings 30 spaced along an upper end lower arm. A conduit 32 connects each valve 10 with the header 34 of a low-pressure water system (not shown). A multiplate pressure-reducing orifice 36 is disposed in the conduit 32 adjacent the end thereof toward the valve 10 for reducing the pressure of the water flowing through the conduit to a pressure compatible with the low-pressure system connected with the header 34. A type of pressure-reducing device suitable for this purpose which is available on the market is manufactured by Worthington Corporation of Harrison, New Jersey, and is designated Worthington Multiplate Pressure Reducing Orifice(various) Psi Series. A gate valve 38 and a check valve 40 are disposed in spaced relation in each conduit 32 adjacent the end thereof connected with the header 34. The check valve 40 restricts the flow of water in the conduit 32 to the diretcion toward the header 34. Another conduit 42 in each spray system 8 connects the conduit 26 with the conduit 32 for supplying low-pressure water to the spray nozzle head 28 from the conduit 32 so as to maintain the nozzle head full of Water when the head is not being used for descaling, for a reason which will become apparent hereinafter. A gate valve 44 and a check valve 46 are disposed in spaced relation in the conduit 42 adjacent the end thereof toward the conduit 26. Check valve 46 restricts the flow of water through conduit 42 to the direction toward the conduit 26.

A gate valve 48 may be disposed between the pump 2 and the header 4 for shutting off the flow of water into the header when desired. Gate valves 24, 38, 44 and 48 are kept open at all times during operation of the system of the invention.

In operation, water under a constant, predetermined pressure (for example, approximately 2,000 psi. for descaling purposes) is delivered by pump 2 into the header 4. The water flows from the header 4 into each of the valves at the predetermined, constant pressure. In the exemplary embodiment of the invention shown in the diagrammatic illustration of the drawing, the valve 10 at each end of the diagram are shown shifted to the left and are feeding high-pressure water into conduits 26 from outlet ports 16. Conduits 26 conduct the Water at undirninished pressure to the spray nozzle heads 28 from whence it issues from spray openings 30 to descale billets B. Conduit 32 is blocked at the valve 10.

The valve 10 of the intermediate spray system 8 in the diagram of the drawing is shown shifted to the left.

With the valve in this position, conduit 26 is blocked at valve 10 and water at the predetermined high pressure is flowing into the conduit 32. As the water flows through the pressure-reducing orifice 36 in the conduit 32, its pressure is reduced to a pressure compatible with the requirements of a low-pressure system connected with the header 34. Most of the water flowing through conduit 32 flows through the check valve 40 and gate valve 38 into header 34. However, some of the water flowing through conduit 32 return-flows into conduit 42 and flows through gate valve 44 and check valve 46 into conduit 26 from whence it flows into the idle spray nozzle head 28. During periods of no descaling demand, the spray nozzle heads not operating, such as the intermediate spray nozzle head 28 of the drawing, are continuously maintained full of water by return flow, as described above, through conduit 42 and gate valve 44 and check valve 46. If the spray nozzle heads were permitted to drain during periods of no descaling demand, the sudden inru-sh of water at high pressure into an empty nozzle head would cause severe line shock.

Although I have shown three water spray systems in the exemplary embodiment of the hydraulic system of my invention illustrated in the drawing, it will be understood that more or less than three water spray systems may be included in the hydraulic system of my invention, as desired.

It will now be clearly seen that the fluid pressure at the demand points of the hydraulic system of my in vention will remain uniform and constant notwithstanding the number and combinations of demand points or descaling heads operating. It will be further apparent that the constant flow of water through the system of the invention is unaffected by the number and combination of outlets operating so that shock in the system is prevented when the number and combinations of operating outlets is changed during operation of the system.

While one embodiment of my invention has been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. A constant pressure, variable demand hydraulic system comprising a source of fluid under pressure, a header connected with said source, a plurality of fluid spray systems connected with and drawing fluid from said header, each of said fluid spray systems including a constant-flow, two-position fluid valve having an inlet port and first and second outlet ports connected at its inlet port with said header, said valve being adapted to be shifted between one position wherein said first outlet port is open and said second outlet port is closed and another position wherein said second outlet port is open and said first outlet port is closed without diminishing the flow of fluid through said valve, a first fluid conduit connected by one end with said first outlet port and by its other end with a fluid disposal means, pressure-reducing means in said first conduit adjacent said one end thereof for reducing the pressure of fluid flowing into said conduit from said first outlet, a second conduit connected by one end with said second fluid port, fluid spray nozzle means connected with the other end of said second conduit, a third conduit extending between said first conduit and said second conduit for conducting fluid under reduced pressure to said nozzle means from said first conduit when said first outlet port is open, a first check valve in said third conduit restricting the flow of fluid therethrough to the direction toward said second conduit, and a second check valve in said first conduit restricting the flow of fluid therethrough to the direction toward said fluid disposal means.

2. Apparatus as defined by claim 1 in which said pressure-reducing means comprises a multi-plate orifice.

3. Apparatus as defined by claim 1 in which a shut-off valve is interposed in said third conduit between said first check valve and said first conduit.

4. Apparatus as defined by claim 1 in which a shut-off valve is interposed in said first conduit between said fluid disposal means and said second check valve.

No references cited.

EVERETT W. KIRBY, Primary Examiner. 

1. A CONSTANT PRESSURE, VARIABLE DEMAND HYDRAULIC SYSTEM COMPRISING A SOURCE OF FLUID UNDER PRESSURE, A HEADER CONNECTED WITH SAID SOURCE, A PLURALITY OF FLUID SPRAY SYSTEMS CONNECTED WITH AND DRAWING FLUID FROM SAID HEADER, EACH OF SAID FLUID SPRAY SYSTEMS INCLUDING A CONSTANT-FLOW, TWO-POSITION FLUID VALVE HAVING AN INLET PORT AND FIRST AND SECOND OUTLET PORTS CONNECTED AT ITS INLET PORT WITH SAID HEADER, SAID VALVE BEING ADAPTED TO BE SHIFTED BETWEEN ONE POSITION WHEREIN SAID FIRST OUTLET PORT IS OPEN AND SAID SECOND OUTLET PORT IS CLOSED AND ANOTHER POSITION WHEREIN SAID SECOND OUTLET PORT IS OPEN AND SAID FIRST OUTLET PORT IS CLOSED WITHOUT DIMINISHING THE FLOW OF FLUID THROUGH SAID VALVE, A FIRST FLUID CONDUIT CONNECTED BY ONE END WITH SAID FIRST OUTLET PORT AND BY ITS OTHER END WITH A FLUID DISPOSAL MEANS, PRESSURE-REDUCING MEANS IN SAID FIRST CONDUIT ADJACENT SAID ONE END THEREOF FOR REDUCING THE PRESSURE OF FLUID FLOWING INTO SAID CONDUIT FROM SAID FIRST OUTLET, A SECOND CONDUIT CONNECTED BY ONE END WITH SAID SECOND FLUID PORT, FLUID SPRAY NOZZLE MEANS CONNECTED WITH THE OTHER END OF SAID SECOND CONDUIT, A THIRD CONDUIT EXTENDING BETWEEN SAID FIRST CONDUIT AND SAID SECOND CONDUIT FOR CONDUCTING FLUID UNDER REDUCED PRESSURE TO SAID NOZZLE MEANS FROM SAID FIRST CONDUIT WHEN SAID FIRST OUTLET PORT IS OPEN, A FIRST CHECK VALVE IN SAID THIRD CONDUIT RESTRICTING THE FLOW OF FLUID THERETHROUGH TO THE DIRECTION TOWARD SAID SECOND CODUIT, AND A SECOND CHECK VALVE IN SAID FIRST CONDUIT RESTRICTING THE FLOW OF FLUID THERETHROUGH TO THE DIRECTION TOWARD SAID FLUID DISPOSAL MEANS. 